1. Field of the Invention
The present invention refers to the field of connectors for optical cables. It relates to an optical connector according to the preamble of claim 1.
2. Description of Prior Art
For outside applications, such as in base stations or antennas of mobile radio networks, on ships, for industrial cable and fibre-optic installations or the like, where harsh environmental conditions prevail, optical connectors, which are matched to the particular requirements in terms of application and behaviour, are available under the designation ODC (Outdoor Connector) (see for example the article “ODC—Ein Verbinder für die harten Applikationen” [ODC—A connector for the hard applications] Connectivity News January 2007 (Huber+Suhner), pages 10-11).
In these known connectors, which are designed for a water-tight and dust-tight connection of two or four cable pairs and use compact ferrules with an external diameter of 1.25 mm for each optical fibre, and which use prefabricated connector inserts (termini), as are disclosed for example in EP-B1-1 254 387 (see FIGS. 3 and 4 therein), a screw lock in which a union nut attached to a connector portion is screwed onto an external thread arranged on the other connector portion is used for securing the connection in the inserted state. The termini are inserted into and directly held by a robust outer housing of the connector.
Such a screw lock has various disadvantages, however:                The reliability of the lock is limited because the screw connection can be released if vibrations or the like occur. In particular, the quality of the screw connection depends on whether the union nut is screwed correctly onto the thread; consequently, mounting defects can arise.        The screw lock requires a significant outlay in terms of time, which is of particular consequence if a large number of optical connections must be produced at one location.        Specific tools (e.g. torque wrench) which cause additional costs and organizational outlay are necessary for the correct screw connection with predefined tightening torque.        In order to provide tools with sufficient access to the screw connection, the minimum distance between neighbouring connections must be chosen to be large enough for the achievable connector density to be limited thereby.        The screw connection results in abrasion on the threads, which can have a negative effect on the very sensitive optical connection. Furthermore, a corrosion-protection coating applied to the connector can be removed.        The screw connection causes the connector to be loaded with a high torque, which must be absorbed by a means of protection against rotation and deteriorates the rotary (polar) orientation in the circumferential direction.        
On the other hand, it has long been known in the field of electric connectors, in particular for coaxial lines, to use quick-release locks, which operate with a locking ring which latches, when inserted into an annular groove, on the counterpart and can be released again by means of a specific actuating element (see for example DE-A1-2 353 004 or EP-A1-0 491 626). Similar quick-release locks have also been used in flexible-tube connections for a long time.
However, optical connections differ from (coaxial) electric connections or flexible-tube connections by virtue of an essential feature: the ends (usually supported in specific ceramic ferrules) of the optical fibres to be connected bluntly strike each other during the connection process, whereas a gliding contact connection or line connection occurs in the electric or flexible-tube connections.
Optical connectors are compared to coaxial electrical connectors a completely different class of connectors, which need to fulfil different criteria: One major aspect is the need that the optical fibres arranged inside of the connector must coaxially match with each other in a very limited tolerance. In difference to, for example, a connector for a coaxial cable, having a centre core and an outer shield to be interconnected at minimum electromagnetic disturbance, an optical connector must guarantee that the one or more single optical wires are interconnected to each other frontal (face to face). Thereby the connection must be guaranteed at different temperature levels, humidity, vibrations and outside influences upon the outer casing of the connector such as pulling on the cable, etc. A further issue is, that these connectors must fulfil certain limitations with respect to dimensions often caused by historical standards. Thereby the space available is very limited. E.g. it must be possible to insert the connectors into bores, which have a given diameter and spacing.